Wireless biosensor system for real-time cholesterol monitoring in fish "Nile tilapia"

Lipidest: a lipid profile screening test under extreme point of care settings using a portable spinning disc and an office scanner

The demand for lipid profile (the cholesterol and triglyceride elements in the blood) testing outside resourced diagnostic centers is continuously increasing for personalized and community-based healthcare to ensure timely disease screening and management; however, it is inevitably challenged by several bottlenecks in the existing point of care technologies. These deficits include delicate sample pre-processing steps and device complexity, which give rise to unfavourable cost propositions to safeguard against compromised test accuracy. To circumvent these bottlenecks, herein, we introduce a new diagnostic technology, 'Lipidest', that integrates a portable spinning disc, a spin box, and an office scanner to reliably quantify the complete lipid panel from finger-prick blood. Our design facilitates the direct miniature adaptation of the established gold standard procedures as against any indirect sensing technologies that are otherwise common in point-of-care applications introduced commercially. The test procedure harmoniously connects all the elements of sample-to-answer integration in a single device, traversing the entire pipeline of the physical separation of plasma from the cellular components of the whole blood, the automated mixing with the test reagents on the same platform in situ, and office-scanner-adapted quantitative colorimetric analytics that eliminate any undesirable artefacts on account of variabilities in the background illumination and camera specifications. The exclusive value of eliminating sample preparation steps, including the rotationally actuated segregation of the specific blood constituents without any cross-interference between them, their automated homogeneous mixing with the respective test reagents, and the simultaneous, yet independent, quantitative readout without specialized instrumentation, render the test user-friendly and deployable in resource-constrained settings with a reasonably wide detection window. The extreme simplicity and modular nature of the device further make it amenable to mass manufacturing without incurring unfavourable costs. Extensive validation with laboratory-benchmark gold standards provide acceptable accuracy and indicates the value of the first-of-its-kind ultra-low-cost extreme-point-of-care test with a scientific foundation akin to highly accurate laboratory-centric technologies for cardiovascular health monitoring and beyond.

Sensitive electrochemical detection of cholesterol using a portable paper sensor based on the synergistic effect of cholesterol oxidase and nanoporous gold

As a crucial biomarker for some diseases, the determination of cholesterol in human serum is of great significance for the diagnosis and prevention of these diseases. Hence, a portable cholesterol detection method is necessary for clinical and domestic applications. Here, a portable paper sensor was designed for cholesterol detection by modifying screen-printed electrode (SPE) with nanoporous gold (NPG). To achieve the reliable cholesterol detection, a synergistic strategy was proposed based on the oxidation of cholesterol by cholesterol oxidase (ChOx) and the reduction of oxidation product (H₂O₂) by NPG. Compared to existing electrochemical sensors, the resulting paper sensor exhibited a wider linear response in a range from 50 μM to 6 mM as well as a higher sensitivity of 32.68 μA mM^-1 cm^-2 with a lower detection limit of 8.36 μM. Moreover, the portable paper sensor presented strong anti-interference capability and stability in the detection of cholesterol in human serum, and the data detected by the portable paper sensor were consistent with that obtained by an automatic biochemical analyzer. These unique performances confirmed that the proposed paper sensor was a sensitive, reliable, and portable cholesterol detection method, making it a good choice for cholesterol detection.

A Self-Powered Glucose Biosensor Operated Underwater to Monitor Physiological Status of Free-Swimming Fish

The changes in blood glucose levels are a key indicator of fish health conditions and are closely correlated to their stress levels. Here, we developed a self-powered glucose biosensor (SPGB) consisting of a needle-type enzymatic biofuel cell (N-EFC), which was operated underwater and connected to a charge pump integrated circuit (IC) and a light emitting diode (LED) as the indicator. The N-EFC consisted of a needle bioanode, which was inserted into the caudal area of a living fish (Tilapia) to access biofuels, and a gas-diffusion biocathode sealed in an airtight bag. The N-EFC was immersed entirely in the water and connected to a charge pump IC with a capacitor, which enabled charging and discharging of the bioelectricity generated from the N-EFC to blink an LED. Using a smartphone, the glucose concentration can be determined by observing the LED blinking frequencies that are linearly proportional to the blood glucose concentration within a detection range of 10–180 mg/dL. We have successfully demonstrated the feasibility of the SPGB used to continuously monitor the physiological status of free-swimming fish treated with cold shock in real time. The power generated by a free-swimming fish with an N-EFC inserted into its caudal area, swimming in a fish tank with a water temperature (Tw) of 25 °C, exhibited an open circuit voltage of 0.41 V and a maximum power density of 6.3 μW/cm2 at 0.25 V with a current density of 25 μA/cm2. By gradually decreasing Tw from 25 °C to 15 °C, the power generation increased to a maximum power density of 8.6 μW/cm2 at 0.27 V with a current density of 31 μA/cm2. The blood glucose levels of the free-swimming fish at 25 °C and 15 °C determined by the blinking frequencies were 44 mg/dL and 98 mg/dL, respectively. Our proposed SPGB provides an effective power-free method for stress visualization and evaluation of fish health by monitoring a blinking LED through a smartphone.

Lipase, Phospholipase, and Esterase Biosensors (Review)

A biosensor is a device composed by a biological recognition element and a transducer that delivers selective information about a specific analyte. Technological and scientific advances in the area of biology, bioengineering, catalysts, electrochemistry, nanomaterials, microelectronics, and microfluidics have improved the design and performance of better biosensors. Enzymatic biosensors based on lipases, esterases, and phospholipases are valuable analytical apparatus which have been applied in food industry, oleochemical industry, biodegradable polymers, environmental science, and overall the medical area as diagnostic tools to detect cholesterol and triglyceride levels in blood samples. This chapter reviews recent developments and applications of lipase-, esterase-, and phospholipase-based biosensors.

Real Time Analysis of Bioanalytes in Healthcare, Food, Zoology and Botany

The growing demand for real time analysis of bioanalytes has spurred development in the field of wearable technology to offer non-invasive data collection at a low cost. The manufacturing processes for creating these sensing systems vary significantly by the material used, the type of sensors needed and the subject of study as well. The methods predominantly involve stretchable electronic sensors to monitor targets and transmit data mainly through flexible wires or short-range wireless communication devices. Capable of conformal contact, the application of wearable technology goes beyond the healthcare to fields of food, zoology and botany. With a brief review of wearable technology and its applications to various fields, we believe this mini review would be of interest to the reader in broad fields of materials, sensor development and areas where wearable sensors can provide data that are not available elsewhere.

Lab-on-a-bird: biophysical monitoring of flying birds

The metabolism of birds is finely tuned to their activities and environments, and thus research on avian systems can play an important role in understanding organismal responses to environmental changes. At present, however, the physiological monitoring of bird metabolism is limited by the inability to take real-time measurements of key metabolites during flight. In this study, we present an implantable biosensor system that can be used for continuous monitoring of uric acid levels of birds during various activities including flight. The system consists of a needle-type enzymatic biosensor for the amperometric detection of uric acid in interstitial fluids. A lightweight two-electrode potentiostat system drives the biosensor, reads the corresponding output current and wirelessly transfers the data or records to flash memory. We show how the device can be used to monitor, in real time, the effects of short-term flight and rest cycles on the uric acid levels of pigeons. In addition, we demonstrate that our device has the ability to measure uric acid level increase in homing pigeons while they fly freely. Successful application of the sensor in migratory birds could open up a new way of studying birds in flight which would lead to a better understanding of the ecology and biology of avian movements.

Development of mediator-type biosensor to wirelessly monitor whole cholesterol concentration in fish

We developed a wireless monitoring system to monitor fish condition by tracking the change in whole cholesterol concentration. The whole cholesterol concentration of fish is a source of steroid hormones or indicator of immunity level, which makes its detection important for tracking physiological condition of fish. Wireless monitoring system comprises of mediator-type biosensor and wireless transmission device. Biosensor is implantable to fish body, and transmission device is so light, in that fish is allowed to swim freely during monitoring. Cholesterol esterase and oxidase were fixated on to the detection site of biosensor and used to detect the whole cholesterol concentration. However, cholesterol oxidase incorporates oxidation-reduction reaction of oxygen for detection, which concentration fluctuates easily due to change in environmental condition. Meanwhile, mediator-type biosensor enables monitoring of whole cholesterol concentration by using mediator to substitute that oxidation-reduction reaction of oxygen. Characteristic of fabricated mediator-type biosensor was tested. The sensor output current of mediator-type biosensor remained stable compared to output current of non-mediator-type biosensor under fluctuating oxygen concentration of 0-8 ppm, which implied that this sensor is less affected by change in dissolved oxygen concentration. That biosensor was then implanted into fish for wireless monitoring. As a result, approximately 48 h of real-time monitoring was successful.

Wireless biosensor system for real-time L-lactic acid monitoring in fish

We have developed a wireless biosensor system to continuously monitor L-lactic acid concentrations in fish. The blood L-lactic acid level of fish is a barometer of stress. The biosensor comprised Pt-Ir wire (φ0.178 mm) as the working electrode and Ag/AgCl paste as the reference electrode. Lactate oxidase was immobilized on the working electrode using glutaraldehyde. The sensor calibration was linear and good correlated with L-lactic acid levels (R = 0.9959) in the range of 0.04 to 6.0 mg · dL(-1). We used the eyeball interstitial sclera fluid (EISF) as the site of sensor implantation. The blood L-lactic acid levels correlated closely with the EISF L-lactic acid levels in the range of 3 to 13 mg · dL(-1) (R = 0.8173, n = 26). Wireless monitoring of L-lactic acid was performed using the sensor system in free-swimming fish in an aquarium. The sensor response was stable for over 60 h. Thus, our biosensor provided a rapid and convenient method for real-time monitoring of L-lactic acid levels in fish.

Lipase and phospholipase biosensors: a review

Recent advances in the field of biology, electronics, and nanotechnology have improved the development of biosensors. A biosensor is a device composed of a biological recognition element and a sensor element. Biosensor applications are becoming increasingly important in areas such as biotechnology, pharmaceutics, food, and environment. Lipases and phospholipases are enzymes which have been used widely in food industry, oleochemical industry, biodegradable polymers, detergents, and other applications. In the medical industry, lipases and phospholipases are used as diagnostic tools to detect triglycerides, cholesterol, and phospholipids levels in blood samples. Therefore, the development of lipase and phospholipase biosensors is of paramount importance in the clinical area. This chapter introduces the reader into the preliminaries of biosensor and reviews recent developments of lipase and phospholipase biosensors.

Edge-plane microwire electrodes for highly sensitive H₂O₂ and glucose detection

The promise of implantable electrochemical sensors is often undermined by the critical requirement of device miniaturization that inadvertently degrades sensor performance in terms of sensitivity and selectivity. Herein, we report a novel miniaturized and flexible amperometric sensor grown at the 'edge plane' of a 25-μm gold wire. Such geometry affords extreme miniaturization along with ease of fabrication, minimal iR drop and 3-D diffusion for effective mass transfer. This together with electrochemical rebuilding of the Au working electrode and subsequent Pt nanoparticles deposition resulted in the highest H2O2 sensitivity (33 mA mM(-1) cm(-2)), reported thus far. Concurrent electrodeposition of o-phenylenediamine with glucose oxidase afforded glucose detection at these edge-plane microsensors with a six fold improvement in sensitivity (1.2 mA mM(-1) cm(-2)) over previous reports. In addition, these sensors exhibit low operation potential (0.3 V), high selectivity (more than 95%) against in vivo interferences, and an apparent Michealis-Menten constant (K(m)(app)) of 17 and 75 mM of glucose in the absence and presence of an outer polyurethane coating, respectively. These features render the edge-plane sensor architecture as a powerful platform for next-generation implantable biosensors.

Switch-based biosensors: a new approach towards real-time, in vivo molecular detection

Although the ability to monitor specific molecules in vivo in real-time could revolutionize many aspects of healthcare, the technological challenges that stand in the way of reaching this goal are considerable and are poorly met by most existing analytical approaches. Nature, however, has already solved the problem of real-time molecular detection in complex media by employing biomolecular "switches". That is, protein and nucleic acids that sense chemical cues and, by undergoing specific, binding-induced conformational changes, transduce this recognition into high-gain signal outputs. Here, we argue that devices that employ such switches represent a promising route towards versatile, real-time molecular monitoring in vivo.